1. Field of the Invention
The present invention relates to a tactile sensor that detects force (pressure) applied to an attachment surface and a gripping robot using the tactile sensor that detects contact pressure, and more specifically, to the tactile sensor suitable for detecting three component forces (in the X direction, Y direction, and Z direction) with high accuracy from small force and the gripping robot using the same.
2. Description of the Related Art
As a tactile sensor of the kind attachable to a fingertip, there is one used in a “soft object grip device” disclosed in Japanese Patent Laid-Open Application No. Hei 8-323678, as an example. This sensor detects contact areas with a lot of minute ON/OFF switches provided therein. The sensor is intended to realize optimal gripping of an object by recognizing size and flexibility of the object from the relation between the detected contact areas and distances between fingertips. The sensor principally detects the force in the vertical direction (Z direction) to the attachment surface.
As a marketable product supplied in the market, there is a pressure distribution measurement system using a film sensor by Nitta Corporation, which uses a sensor sheet for measuring pressure distribution within a surface. The system is intended to measure high-density pressure distribution with the sensor sheet, whereas,  the measurement is effective only for the pressure distribution in the Z direction as well.
In the “force detector” disclosed in Japanese Patent Laid-Open Application No. 2002-181640, there is shown a capacitance-operated force detection. This detector can detect the force in the X direction in addition to the force in the Z direction. The detection of the force in the Z direction is performed on the basis of ON/OFF switches, having limitations as force detection.
The “inner force sensor” disclosed in Japanese Patent Laid-Open Application No. 2000-266620 is constituted to be able to detect a total of six component forces consisting of the forces in the three directions and moments along three axes. The sensor has a structure in which strain gauges are mounted on a three-dimensional crucial rigid body. It is therefore impossible to attach the sensor to a surface of a skin or a fingertip because of the structure. In addition, it is considered that the sensor is unsuitable to detect small force with high accuracy due to the rigid body used therein.                [Patent document 1] JP-A 8-323678        [Patent document 2] JP-A 2002-181640        [Patent document 3] JP-A 2000-266620        